Comparison of Different Methods of Reference Evapotrantranspiration Based on Radiation Methods in different Iran climate condition

This study was conducted to compare the evaluation methods of the reference Evapotranspiration for the methods based on solar radiation with FAO Penman Monteith for different climates and the determination of the best model for each weather station and each climate in Iran. The evapotranspiration equations used in this research were Turc, modified Turc, Hargreaves, Makkink models, Priestley-Taylor, Jensen- Haise, McGuinness & Bordne, Jones & Ritchie, Irmak, Hansen, Doorenbos- Pruitt, Abtew, and tabari et all models. Meteorological data from 154 synoptic stations across the country on a daily basis was prepared from the country's Meteorological Agency for 15 years. The accuracy of the methods was evaluated using the RMSE, MBE, R and t statistics. The comparative results of this study showed that models of Hansen and modified Abtew were more applicable and Jones & Ritchie and Hargreavs had the less accuracy in arid climates. In semi-arid areas Irmak and Hansen methods had more accuracy. In Mediterranean areas Adjusted Turk and Makkink 2 were more accurate methods. In the semi- humid, humid and very humid areas the methods of Priestley-Taylor and Irmak presented more appropriate results. The methods of Jones & Ritchie and Doorenbos – Pruitt were the less accuracy in all climates.